Mechanical properties of reaction sintered SiC-TiC composite

SiC-TiC composite containing 5-30 vol% TiC particles was fabricated by conversion of TiO2 to TiC during pressureless sintering. The presence of very fine and uniformly distributed, in-situ created TiC particles increased driving force for sintering allowing fabrication of high density SiC-TiC composite without the use of external pressure. The highest mechanical properties were measured in samples sintered at 1885 degrees C for 1 h. The highest values for hardness (similar to 20 GPa) and fracture strength (similar to 490 MPa) were measured in samples containing 5 vol% TiC, whereas the highest fracture toughness (similar to 5.5 MPa.m(1/2) ) was measured in samples containing 10 vol% TiC. The presence of in-situ created, uniformly distributed TiC particles was beneficial for activation of not only the crack deflection mechanism but also mechanism called toughening by residual stress crated due to the difference of thermal expansion between SiC matrix and TiC particles. The compressive stress field around TiC particles acts to close the propagating crack and thus to increase fracture toughness.